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Name ________________ Unit 7 Gases and the Kinetic Molecular Theory -1- Name ________________ Assignment Chemistry: Unit 7 Outline: Gas Las WB Page Must be done Number at school Podcast 7.1 Intro to Gases Worksheet 7.1 Podcast 7.2 Gas Laws Worksheet 7.2 Lab: Boyles Law Take Home Lab: Pressure and Balloons Lab: Charles’ Law Podcast 7.3 Combined Gas Law Worksheet 7.3 Podcast 7.4 Ideal Gas Law Worksheet 7.4 Podcast 7.5 Graham’s and Dalton’s Laws Worksheet 7.5 Demo: Graham’s Law Podcast 7.6 Gas Stoichiometry Worksheet 7.6 Lab: Stoichiometry and Gas Laws Podcast 7.7 Molar Mass of Gas Worksheet 7.7 Unit 7 Review Lab Test: MM of Butane Unit 7 Exam Online Teacher Handout Pg 12-13 Online Pg 4-5 x Pg 6-8 Pg 14-15 Online Teacher Demo Pg 16 x x Pg 9-11 x Pg 19-21 Pg 22 In class In class x x -2- Done? Name ________________ Unit 7 Vocabulary Boyle’s Law Charles’s Law Gay-Lussac’s Law Combined Gas Law Ideal Gas Law Ideal Gas Constant (R) Dalton’ s Law of Partial Pressures Effusion Graham’s Law of effusion Diffusion -3- Name ________________ Take Home Lab: Gas Laws Purpose: To determine the atmospheric pressure at a location that has a different altitude than Woodland Park. Materials: A balloon, a tape measure, and a string Procedure: 1. Blow up a balloon either at a lower altitude (Colorado Springs) or a higher altitude (Woodand Park), and take the balloon to the other location. You could also fill the balloon up in Woodland Park and then go skiing and measure the diameter of the balloon at the top of Hosier Pass. 2. Measure the circumference of the balloon in the first location. This is probably best done with a string. 3. Drive to location 2 and measure the circumference of the balloon. Calculations: 1. In the interest of making the calculations simple, we will assume that the balloon is a sphere. 2. Using the equation C=2πr, determine the radius of the balloon in both locations. 3. Using the equation V=4/3πr3, determine the volume of the balloon in both locations. 4. Assuming that the pressure in Woodland Park is 571 torr, determine, using Boyles Law, the pressure in location 2. 5. Use the table on the next page to determine your percent error. You may need to use a program like google earth to determine the altitude for your two samples. The graph below only shows form about 6500 feet up to 15,000 feet. The pressure unit is in millibars: 1mb = 0.75 torr Data Table Circumference of Balloon at lower Altitude Radius of balloon at lower altitude Volume of balloon at lower altitude Circumference of Balloon at higher Altitude Radius of balloon at higher altitude Volume of balloon at higher altitude Pressure in Woodland Park 571 torr Pressure at Location 2 -4- Name ________________ Questions 1. Discuss, using the kinetic molecular theory, why the balloon shrunk or grew at different altitudes. Use a picture in your explanation. 2. What would happen if you took your balloon to the top of Mt. Everest (average pressure = 253torr), the tallest point on the earth? 3. Explain why air pressure goes down the higher you are in altitude. For Credit: You must have a signed note from your parent/guardian explaining two things: 1. Why does air pressure go down as you go up in altitude 2. Why does a bag of potato chips purchased in Colorado Springs expand (and sometimes, blow up) when brought to Woodland Park? -5- Name ________________ Boyle’s Law: Pressure-Volume Relationship in Gases The primary objective of this experiment is to determine the relationship between the pressure and volume of a confined gas. The gas we use will be air, and it will be confined in a syringe connected to a Gas Pressure Sensor (see Figure 1). When the volume of the syringe is changed by moving the piston, a change occurs in the pressure exerted by the confined gas. This pressure change will be monitored using a Gas Pressure Sensor. It is assumed that temperature will be constant throughout the experiment. Pressure and volume data pairs will be collected during this experiment and then analyzed. From the data and graph, you should be able to determine what kind of mathematical relationship exists between the pressure and volume of the confined gas. Historically, this relationship was first established by Robert Boyle in 1662 and has since been known as Boyle’s law. OBJECTIVES In this experiment, you will Use a Gas Pressure Sensor and a gas syringe to measure the pressure of an air sample at several different volumes. Determine the relationship between pressure and volume of the gas. Describe the relationship between gas pressure and volume in a mathematical equation. Use the results to predict the pressure at other volumes. Figure 1 MATERIALS LabQuest LabQuest App Vernier Gas Pressure Sensor 20 mL gas syringe PROCEDURE 1. Prepare the Gas Pressure Sensor and an air sample for data collection. a. Connect the Gas Pressure Sensor to LabQuest and choose New from the File menu. If you have an older sensor that does not auto-ID, manually set up the sensor. b. With the 20 mL syringe disconnected from the Gas Pressure Sensor, move the piston of the syringe until the front edge of the inside black ring (indicated by the arrow in Figure 1) is positioned at the 10.0 mL mark. c. Attach the 20 mL syringe to the valve of the Gas Pressure Sensor. 2. Set up the data-collection mode. a. On the Meter screen, tap Mode. Change the mode to Events with Entry. b. Enter the Name (Volume) and Units (mL). Select OK. -6- Name ________________ 3. To obtain the best data possible, you will need to correct the volume readings from the syringe. Look at the syringe; its scale reports its own internal volume. However, that volume is not the total volume of trapped air in your system since there is a little bit of space inside the pressure sensor. To account for the extra volume in the system, you will need to add 0.8 mL to your syringe readings. For example, with a 5.0 mL syringe volume, the total volume would be 5.8 mL. It is this total volume that you will need for the analysis. 4. You are now ready to collect pressure and volume data. It is easiest if one person takes care of the gas syringe and another enters volumes. a. Start data collection. b. Move the piston so the front edge of the inside black ring (see Figure 2) is positioned at the 5.0 mL line on the syringe. Hold the piston firmly in this position until the pressure value displayed on the screen stabilizes. c. Tap Keep and enter 5.8, the gas volume (in mL) on the screen. Remember, you are adding 0.8 mL to the volume of the syringe for the total volume. Select OK to store this pressurevolume data pair. Figure 2 d. Continue this procedure using syringe volumes of 10.0, 12.5, 15.0, 17.5, and 20.0 mL. e. Stop data collection. 5. When data collection is complete, a graph of pressure vs. volume will be displayed. To examine the data pairs on the displayed graph, tap any data point. As you tap each data point, the pressure and volume values are displayed to the right of the graph. Record the pressure and volume data values in your data table. 6. Based on the graph of pressure vs. volume, decide what kind of mathematical relationship exists between these two variables, direct or inverse. To see if you made the right choice: a. Choose Curve Fit from the Analyze menu. b. Select Power as the Fit Equation. The curve fit statistics for these two data columns are displayed for the equation in the form y = Ax^B where x is volume, y is pressure, A is a proportionality constant, and B is the exponent of x (volume) in this equation. Note: The relationship between pressure and volume can be determined from the value and sign of the exponent, B. c. If you have correctly determined the mathematical relationship, the regression line should very nearly fit the points on the graph (that is, pass through or near the plotted points). d. Select OK. 7. (optional) If directed by your instructor, proceed directly to the Extension that follows Processing the Data. -7- Name ________________ DATA AND CALCULATIONS Volume (mL) Pressure (kPa) Constant, k (P / V or P • V) PROCESSING THE DATA 1. If the volume is doubled from 5.0 mL to 10.0 mL, what does your data show happens to the pressure? Show the pressure values in your answer. 2. If the volume is halved from 20.0 mL to 10.0 mL, what does your data show happens to the pressure? Show the pressure values in your answer. 3. If the volume is tripled from 5.0 mL to 15.0 mL, what does your data show happened to the pressure? Show the pressure values in your answer. 4. From your answers to the first three questions and the shape of the curve in the plot of pressure versus volume, do you think the relationship between the pressure and volume of a confined gas is direct or inverse? Explain your answer. 5. Based on your data, what would you expect the pressure to be if the volume of the syringe was increased to 40.0 mL. Explain or show work to support your answer. 6. Based on your data, what would you expect the pressure to be if the volume of the syringe was decreased to 2.5 mL. 7. What experimental factors are assumed to be constant in this experiment? 8. One way to determine if a relationship is inverse or direct is to find a proportionality constant, k, from the data. If this relationship is direct, k = P/V. If it is inverse, k = P•V. Based on your answer to Question 4, choose one of these formulas and calculate k for the seven ordered pairs in your data table (divide or multiply the P and V values). Show the answers in the third column of the Data and Calculations table. 9. How constant were the values for k you obtained in Question 8? Good data may show some minor variation, but the values for k should be relatively constant. 10. Using P, V, and k, write an equation representing Boyle’s law. Write a verbal statement that correctly expresses Boyle’s law. EXTENSION 1. To confirm that an inverse relationship exists between pressure and volume, a graph of pressure vs. reciprocal of volume (1/volume) may also be plotted. To do this using LabQuest: a. Tap the Table tab to display the data table. -8- Name ________________ b. Choose New Calculated Column from the Table menu. c. Enter the Name (1/Volume) and Units (1/mL). Select the equation, A/X. Use Volume as the Column for X, and 1 as the value for A. d. Select OK. 2. Follow this procedure to calculate regression statistics and to plot a best-fit regression line on your graph of pressure vs. 1/volume: a. b. c. d. Choose Graph Options from the Graph menu. Select Autoscale from 0 and select OK. Choose Curve Fit from the Analyze menu. Select Linear as the Fit Equation. The linear-regression statistics for these two data columns are displayed in the form: y = mx + b where x is 1/volume, y is pressure, m is a proportionality constant, and b is the y-intercept. e. Select OK. If the relationship between P and V is an inverse relationship, the graph of pressure vs. 1/volume should be direct; that is, the curve should be linear and pass through (or near) the origin. Examine your graph to see if this is true for your data. -9- Name ________________ Charles’ Law Lab Purpose: To determine the relationship between Temperature and volume of a gas. Procedure 1. Obtain an empty 250 mL Erlenmeyer flask with a one hole stopper and use crucible tongs to hold it in a boiling how water bath. 2. After 5 min quickly invert the flask (holding your finger over the one hole) and move it into a vat of ice cold water. 3. Remove your finger from the stopper and allow water to move into the flask. 4. Hold the flask under the water for 5 minutes 5. Measure the amount of water in the flask using a graduated cylinder 6. Measure the total amount of water in the flask using a graduated cylinder. 7. Measure the temperature of both the ice water and the boiling water. Safety There is a danger of the flask imploding. You need to make sure that your flask has no chips or cracks. If so report this to your teacher immediately and don’t use that flask. - 10 - Name ________________ Data Total Volume of water in flask Volume of water in flask after the experiment Volume of air in the flask when hot Volume of air in the flask when cold Temperature of the hot gas (˚C) Temperature of the cold gas (˚C) Data Analysis Plot a graph of temperature (x axis) verses Volume (y axis). Set your such that the temperature goes from –400˚C to 200˚C. Set your volume (y axis) to be from 0 to 300 mL Place two points on your graph and draw the line back to where volume is equal to zero. Questions 1. At what point did your line cross the x axis? What is the significance of this point? 2. What happens to molecules at absolute zero? 3. What would really happen to your gas if you cooled it down to a really low temperature? (HINT: Think about attractive forces) 4. What is your percentage error for the determination of absolute zero? - 11 - Name ________________ - 12 - Name ________________ - 13 - Name ________________ Stoichiometry and Gas Law Lab Purpose: To determine the volume of H2 that will be liberated when a sample of magnesium is completely reacted with excess hydrochloric acid (HCl). This is a single replacement reaction. Material: Magnesium ribbon--untarnished, thread, hydrochloric acid--concentrated. Procedure: Fill a plastic tub with water. Roll a length of magnesium ribbon of known mass into a loose coil. Tie it with one end of a piece of thread, approx 25 cm. in length, in such manner that all the loops of coil are tied together. Obtain 5ml. of concentrated hydrochloric acid (DANGER) from your instructor in the eudiometer. Slowly fill it completely with water, being careful not to mix the water and the acid. Lower the magnesium coil into the water in the gas measuring tube to a depth of about 5 cm. Close the tube with your thumb so that the thread is held firmly against the edge of the tube. Taking care that no air enters, invert the eudiometer in the tub and allow it to rest against the bottom to hold the thread. It may be clamped in this position on the ring stand, as shown. When the magnesium has completely reacted (no more metal present and the bubbles have stopped), go to the big bucket of water and insert your tube in the water. Adjust the tube until the liquid levels inside and outside are the same. Read the volume of hydrogen gas liberated as precisely as possible. Take the temperature of the water in the tub and assume this to be temperature of the hydrogen gas collected. Record the barometric pressure from the board. - 14 - Name ________________ Procedure: Turn the paragraphs above into a stepwise procedure. Place an * next to each step whenever a measurement must be recorded in your data table, Data & Calculations: 1. Record all data in the provided table. 2. The mass of one meter of magnesium is ____________. Determine the mass of your sample. 3. Calculate the expected volume of hydrogen gas from your data. Begin with the balanced equation and use the ideal gas law to determine the volume of H2 that should have been collected from the mass of magnesium you started with. 4. Calculate the % error using the calculated volume from question (2) above as the accepted value and your measured volume as the experimental value. Questions: 1. What type of reaction occurred? (single, double, synthesis, decomposition, combustion) 2. Why is it necessary to make a water-vapor correction of the barometer reading in this experiment? 3. If this same experiment were done in Florida, how would the experimental volume (would it be higher or lower) of the gas have changed? Explain thoroughly. 4. Complete a cause-effect error analysis to explain your observed % error. Include a minimum of 4 specific errors. Data Table Length of Mg obtained (cm) Mass of Mg (g) Volume of H2 Actual (mL) Temperature of H2O=THydrogen Atmospheric Pressure (mmHg) Vapor Pressure of H2O (mmHg) Pressure of H2 Volume of H2 Predicted (mL) Percentage Error - 15 - Name ________________ CUT THIS TABLE OUT AND PLACE IT IN YOUR COMPOSITION BOOK Water Vapor Pressure Temp VP Temp ºC mm ºC Hg 4 6.1 27 5 6.5 28 6 7.0 29 7 7.5 30 8 8.0 31 9 8.6 32 10 9.2 33 11 9.8 34 12 10.5 35 13 11.2 36 14 12.0 37 15 12.8 38 16 13.6 39 17 14.5 40 18 15.5 41 19 16.5 42 20 17.5 43 21 18.6 44 22 19.8 45 23 21.0 46 24 22.3 47 25 23.7 48 26 25.2 49 VP mm Hg 26.7 28.3 30.0 31.8 33.6 35.6 37.7 39.8 42.1 44.5 47.0 49.7 52.4 55.3 58.3 61.5 64.8 68.3 71.9 75.6 79.6 83.7 88.0 - 16 - Name ________________ - 17 - Name ________________ Gas Laws Worksheet 7.2: Boyles-Charles-Gay-Lussac 1. You are now wearing scuba gear and swimming under water at a depth of 66.0 ft. You are breathing air at 3.00 atm and your lung volume is 10.0 L. Your scuba gauge indicates that your air supply is low so, to conserve air, you make a terrible and fatal mistake: you hold your breath while you surface. What happens to your lungs? Why? 2. A gas with a volume of 4.0 L at a pressure of 0.90-atm is allowed to expand until the pressure drops to 0.20-atm. What is the new volume? 3. A given mass of air has a volume of 6.0 L at 1.0-atm. What volume will it occupy at 190 mm Hg if the temperature does not change? 4. The pressure of air in an automobile tire is 2.0-atm at 27˚ C. At the end of a journey on a hot sunny day the pressure has risen to 2.2-atm. What is the temperature of the air in the tire? (Assume that the volume of the tire has not changed.) 5. Five liters of air at -50˚C is warmed to 100˚C. What is the new volume if the pressure remains constant? 6. A gas cylinder contains nitrogen gas at 10-atm pressure and a temperature of 20˚C. The cylinder is left in the sun, and the temperature of the gas increases to 50˚C. What is the pressure in the cylinder? - 18 - Name ________________ 7. A bike tire has a volume of 0.850L at a pressure of 40 psi and 0˚C. What will be the pressure of the tire at 35˚C? 8. A hot air balloon has a volume of 10,000-L when at 25˚C. What will be the new volume if the air is heated up to 65˚C? 9. A student holds the end of a bicycle pump and pumps the air in the pump. He holds on for as long as possible. Before pumping the pressure was 20-psi The pressure gauge on the pump reads 80psi right before air escaped. By what fraction did he reduce the volume in the pump. Hint: Assume that you have 1-L of air and use Boyle’s law to determine the number. 10. A tire pressure gauge is used to determine that the pressure in an automobile tire is 25 psi on a cold winter day (-10˚C). After the car has driven a considerable distance the pressure was 30 psi. What is the temperature of the gas inside of the car tire? - 19 - Name ________________ Gas Laws Worksheet 7.3 The Combined Gas Law Worksheet 1. A 5.0L balloon in a freezer is at a temperature of -50˚C has a pressure of 800 mm Hg. What will be the new pressure if the balloon is taken out and placed in a warm room (Temperature 37˚C) and the volume expands to 7.0 L? 2. A 2.0 L bag of potato chips in Denver is at 15˚C and 0.82 atm. The same bag is brought to the top of Longs Peak on a cold winter day. If the bag can only expand to 2.5 L before exploding and Longs Peak has a temperature of -5˚C and a pressure of 0.45 atm, will the bag explode? Use the combined gas law to prove this to yourself. 3. A gas has a volume of 0.50 L, a pressure of 0.5 atm, and a temperature of 40˚C. What will be the new temperature if the gas is expanded to 5.0L L and a pressure of 0.10atm atm? 4. Convert 44.5 L of oxygen at 32˚C and 654 mm Hg to STP. Hint: when STP is stated this gives you a specific temperature and a specific pressure. 5. A gas bubble has a volume of 0.650 mL at the bottom of a lake, where the pressure is 3.46atm. What is the volume of the bubble at the surface of the lake, where the pressure is 1.00atm? Assume that the temperature is constant. Will the new volume be bigger or smaller? - 20 - Name ________________ 6. A balloon filled with air has a volume of 3.25 L at 30°C. It is placed in a freezer at -10°C. What is the volume of the balloon at this temperature? Assume that the pressure is constant. What are the temperatures in Kelvin? Should V2 be bigger or smaller? 7. A .500 L container contains nitrogen gas at 0.800-atm and 0°C. If the highest pressure the container can withstand before exploding is 3.0-atm, what is the highest temperature to which the gas can be heated? Assume the volume is constant. What is the original temperature in Kelvin? Should T2 be bigger or smaller from the change in pressure? 8. A weather balloon is partially filled with helium at 20°C to a volume of 31.5 L and a pressure of 1.3 atm. The balloon rises to the stratosphere, where the temperature is -23°C and pressure is .00300 atm. Calculate the volume of the balloon in the stratosphere. What are the temperatures in Kelvin? What effect does the change in temperature have on V2? What effect does the change in pressure have on V2? Does temperature or pressure have more influence on volume in this balloon? - 21 - Name ________________ Gas Laws Worksheet 7.4: Ideal Gas Law Worksheet 1. What pressure will be exerted by 0.450 mol of a gas at 25˚C if it is contained in a vessel whose volume is 650mL? 2. What volume will 12.0 g of oxygen gas (O2) occupy at 25˚C and a pressure of 0.520 atm? 3. If 4.5 g of methane (CH4) is introduced to an evacuated 2.00L container at 35˚C, what is the pressure in the container in atmospheres? 4. A 5.00 L flask at 25˚ C contains 0.200 mol of Cl2. What is the pressure in the flask? 5. What is the pressure exerted by 32 g of O2 in a 20-L container at 30.0˚C? 6. How many moles of N2 are in a flask with a volume of 250 mL at a pressure of 0.56 atm and a temperature of 300 K? - 22 - Name ________________ WS D: Gas Law Worksheet 7.5: Daltons and Graham’s Law Dalton’s Law Questions 1. A container holds three gases: oxygen, carbon dioxide, and helium. The partial pressures of the three gases are 2.00 atm, 3.00 atm, and 4.00 atm, respectively. What is the total pressure inside the container? 2. A container with two gases, helium and argon, is 30.0% by volume helium. Calculate the partial pressure of helium and argon if the total pressure inside the container is 4.00 atm. 3. If 60.0 L of nitrogen is collected over water at 40.0 °C when the atmospheric pressure is 760.0 mm Hg, what is the partial pressure of the nitrogen? Graham’s Law Questions 4. If equal amounts of helium and argon are placed in a porous container and allowed to escape, which gas will escape faster and how much faster? 5. What is the molecular weight of a gas which diffuses 1/50 as fast as hydrogen? 6. How much faster does hydrogen escape through a porous container than sulfur dioxide? - 23 - Name ________________ Gas Laws Worksheet 7.6: Gas Laws and Stoichiometry Questions 1. Solid potassium chlorate (KClO3) decomposes to produce solid potassium chloride and oxygen gas. What volume of oxygen gas, measured at 40°C and 655 mmHg, will be produced when 13.5 g of potassium chlorate is decomposed? 2. How many grams of water are produced when 500 L of hydrogen gas measured at 25°C and 0.97-atm is ignited with oxygen? 3. If 500 g of carbon disulfide burns in the presence of oxygen to produce carbon dioxide and sulfur dioxide, how many liters of sulfur dioxide collected over water measured at 27°C and 740-mmHg, are produced? 4. C6H12O6 (s) + 6 O2 (g) ---------> 6CO2(g) + 6H2O(g) Given the above reaction, How many grams of C6H12O6 (s) will be needed to make 54 mL of CO2 at 550˚C and 8 atm? - 24 - Name ________________ 5. How many Liters of carbon dioxide is produced at 300 K and 99.2-kPa when 43.65 grams of acetylene, C2H2 is burned? 6. When silicon dioxide reacts with carbon by heating, the following reaction occurs: SiO2(s) + 3C(s) ----------> SiC(s) + 2CO(g) What will be the volume of carbon monoxide collected over water will be produced at 22.0˚C and 657mm when 96.25 grams of SiO2 completely reacts? 7. Nitroglycerine explodes violently to form several gasses according to the following equation: 4 C3H5O9N3 ----------> 12 CO2(g) + O2(g) + 6N2(g) + 10 H2O(g) A sealed 1.00 mL container filled with 2.8 g of nitroglycerine is detonated. If the Temperature inside the container is 300˚C and assuming that the container would not break upon detonation, what is the pressure inside the container right after detonation? (Put your answer in atm's) - 25 - Name ________________ Gas Law Worksheet 7.7: Molar Mass of a Gas 1. A 256 mL sample of an unknown gas was collecte over water at 23˚C and 750 mmHg. The gas has a mass of 0.80 grams. What is the molar mass of the gas? (The vapor pressure of water at 23˚C is 21.0 mmHg) 2. 0.235 grams of magnesium reacts with excess hydrochloric acid to make 309 mL of hydrogen gas at 28˚C and 615 mmHg. (The vapor pressure of water at 28˚C is 28.3 mmHg). From the experimental data what is the molar mass of magnesium? What is the percentage error? 3. 0.855 grams of Potassium chlorate decomposes into oxygen gas and potassium chloride. A 350 mL sample of oxygen gas was collected at 65˚C and 810 mmHg over water. (The vapor pressure of water at 65˚C is 187.5 mmHg). According to experimental data, what is the molar mass of potassium chlorate? What is the percentage of error? 4. A compound contains only nitrogen and hydrogen and is 87.4% nitrogen by mass. A one liter sample of gas has a mass of 0.977 grams at 710 mm Hg and 100˚C. What is the molecular formula of the gas? - 26 - Name ________________ Mixed Gas Law Problems--Review 1. 0.322-g of an unknown gas was collected. The gas had a volume of 59.8-mL a pressure of 655mm Hg and a temperature of 52˚C. What is the molar mass of the gas? 2. A 6.2-L balloon at 55˚C and 615mm Hg is taken to the top of Mt. Everest (-35˚C and 400mmHg). What is the size of the balloon? 3. 2.5-g of oxygen is at 56˚C and 45.3-atm. What is the volume of the gas? 4. 23.5-g of sodium carbonate is reacted with hydrochloric acid to make water, carbon dioxide and sodium chloride. The gas is collected over water at 24˚C and 615-mmHg. What volume is produced? - 27 - Name ________________ 5. 0.21-grams of an unknown gas is collected over water. That gas had a volume of 325-mL and was collected at 744-mm Hg and 21˚C. What is the molar mass of the gas? 6. A bicycle tire that has a volume of 0.85-L is inflated to 140 pounds per square inch. What will be the pressure in the tire if the number of moles of gas is doubled? 7. 324-mL of oxygen is collected over water at 685-mmHg and 18˚C. It is released when hydrogen peroxide (H2O2) decomposes. It also forms water. How many grams of hydrogen peroxide decomposed? 8. Convert 23.5-mL of N2 gas at 220-kPa and 98.7˚C to STP. - 28 - Name ________________ 9. What is the density of oxygen gas at 40˚C and 615-mmHg. Hint: Find the grams per mL. Assume that you have a given amount of grams (You choose) and then convert to volume. Then divide. 10. What is the temperature of a gas that has a volume of 555-mL and 43.5-atm that was initially at 20˚ , 885-mL, and 2.9-atm? 11. At 298 K O2 travels at 1200 miles per hour. What is the speed of Helium at the same temperature? - 29 -